1. Field: The field of the invention is visual aids for positioning towing vehicles for engagement of the hitch with a trailer.
2. Prior Art: Hitches for connecting towing vehicles with trailers typically include a coupling ball upon the vehicle and a mating socket upon a forward projecting tongue of the trailer, both centrally located at bumper level obscured from direct view by the vehicle operator. Hookup requires much trial and error maneuvering,the unaided operator necessarily dismounting repeatedly to check the ball position relative to the socket. Damage to the vehicle or trailer is a real possibility with such blind maneuvering. Many sighting devices have been put forth to solve this problem. Each involves a pair of co-operating visual aids, one secured to the trailer and the other to the towing vehicle, so that alignment of the hitch components may be made by maneuvering of the vehicle from the driver's seat. Representative of these are U.S. Pat. Nos. 3,918,746, 4,285,138 and 4,065,147. Some of the sighting aids are rigidly attached to vehicle or trailer, easily damaged during the vehicle maneuvering for hitching, although some are removably attached with magnets or the like. Some include plumb bobs for precise positioning, for example, perhaps with pivotable sighting rods or the like. Some have built-in illumination. Thus, most of the sighting devices are either impractical, easily damaged beyond use, or are prohibitively expensive. However, all of the sighting aids share a much more serious shortcoming, in that all require vision through the rear window of the towing vehicle, either by way of the inside rear view mirror or by direct sight by the vehicle operator. Many trailer towing vehicles do not provide this unobstructed rear window vision, even if kept uncurtained or uncluttered. Vans often have solid doors in the rear. Some have paired rear doors with opaque edges at the center of the vehicle where vision is needed. In any event, clouding or fouling of the window glass is common. Some hitching assemblies have complicated self-guiding features permitting less precise vehicle positioning (U.S. Pat. Nos. 2,197,157 and 2,844,390). Others have electronic sensors and signal transmitters for blind coupling (U.S. Pat. Nos. 4,432,563 and 4,187,494). There is thus a definite need for a trailer hitching aid which is useful for vehicles without unobstructed rear windows, and which does not require expensive and vulnerable hitching assemblies or electronic apparatus.